The present invention relates generally to a zero insertion force socket for electronic elements having a plurality of electrically conductive pins and in particular to a connector for connecting IC (integrated circuit) elements to a circuit board without damage to the pins thereof.
In the electronic industry, mounting electronic elements (especially IC elements) on circuit boards is a step of importance. Therefore, connectors on which IC elements can be mounted with high efficiency and precision are a bridge for mounting the IC elements to a circuit board in testing and maintaining electronic devices. A connector of poor design usually results in an abnormal signal transmission.
One prior art technique is disclosed in U.S. Pat. No. 4,889,499 filed on 20 May 1988. This patent discloses a plurality of drawbars installed laterally between rows of contacts. Alternate drawbars are caused by an actuator mechanism to slide in opposite directions, thereby engaging the drawbars with one of the two tines of each contact in the rows of contacts on either side of the drawbar. Such a technique has disadvantages that the connector will occupy a large volume since it adds the space of the drawbars and the slidable space thereof. Therefore, the technique is not useful in the future development of the chips with a high density and large number of pins. Further, the connecting construction of the patent is not good enough to provide a close engagement between the pins and the drawbars. As shown in FIGS. 5A and 5B, there are only two engagement points between the pins and the drawbars which will probably result in a poor connection in a short time.
U.S. Pat. No. 4,618,199 teaches a socket for packaging dual in-line pin ICs which comprises a top plate member movable toward and away from a base member. Between the top plate member and the base member, a plurality of U-shaped pin connectors are installed and aligned with the apertures of the top plate member, respectively. The top plate member further comprises a plurality of Y-shaped wedges so that when the top plate member moves toward the base member, the Y-shaped wedges will force the U-shaped pin connectors to permit the pins of the electronic elements to be inserted into the connectors. Such prior art also have disadvantages of poor engagements and large volumes because the engagement points thereof are few and the Y-shaped wedges occupy large volumes.
A prior art socket designed for providing the above-mentioned features is shown in FIGS. 6-11 of the attached drawings. As shown, the socket 1 comprises a plurality of resilient, conductive receptacles 11 which are fixed in a base 12 and are in electrical connection with a circuit board 4. The prior art socket 1 further comprises a slidable block 2 which is disposed on the base 12 and slidable thereon. Each of the receptacles 11 has an expanded section 13 into which one of the pins 31 of an IC element 3 is insertable without electrically contacting the receptacle 11 and a pinching section 14 which has a space less than the size of the pins 31 so that when the one of the pins 31 are in this section, the pin 31 and the receptacle 11 are in electrical connection.
In installing the IC element 3, as shown in FIGS. 6, 8 and 9, the pins 31 of the IC element 3 are first inserted into the expanded sections 13 of the receptacles 11 through associated holes formed on the slidable block 2. Then, as shown in FIGS. 7, 10 and 11, the IC element 3 is forced by the lateral sliding movement of the slidable block 2 to move in such a direction as to have the pins 31 thereof enter the pinching sections 14 of the receptacles 11 and thus be pinched thereby and in electrical connection therewith. To take off the IC element 3, the slidable block 2 is moved in a reverse direction to have the pins 31 disengage with the receptacles 11 so that the IC element 3 can then be taken out of the socket 1 without effort.
This prior art socket, however, has the following disadvantages:
(1) Because of the forcible movement of the pins of the IC element, the pins are more or less bent and undergo shear deformation and thus be damaged. Furthermore, because of the requirement of installing more pins on an IC element, the pins will be designed thinner and weaker and thus increase or aggravate the disadvantage of bending the pins.
(2) Because of the movement of the pins of the IC element, a suitable gap must be preserved between any two successive pins; this has a negative effect in designing IC elements with denser pins.